1. Field of the Invention
The present invention relates in general to devices for assembling catalytic converters, and more particularly to devices for press-fitting a cylindrical catalyzer core bed (or coiled body) into a cylindrical metal case.
2. Description of the Related Art
In order to clarify the task of the present invention, a known technique for press-fitting a cylindrical catalyzer core bed into a cylindrical outer case will be briefly described with reference to FIGS. 13 to 15 of the accompanying drawings. This technique is described in Japanese Patent First Provisional Publication 8-164487.
FIG. 13 shows a method for producing a cylindrical catalyzer core bed (or coiled body) 5 that is a bed for catalyzer. As shown, a flat metal plate 3 and a corrugated metal plate 1 are put on one another and these overlapped plates 3 and 1 are coiled together to form a coiled body 5 which has a circular cross section as shown. After having a brazing foil of Ni (nickel) put around an axially rear end, the coiled body 5 is press-fitted into a cylindrical metal case 7 (see FIGS. 14A and 14B), and then this unit consisting of the coiled body 5 and the metal 7 is led into a vacuum furnace to be subjected to a heat treatment. With this, the flat and corrugated metal plates 3 and 1 are diffusion-bonded and at the same time the coiled body 5 and the cylindrical metal case 7 are brazed.
FIGS. 14A and 14B show a fitting device 13 for press-fitting the coiled body 5 into the cylindrical metal case 7. As shown, the fitting device 13 generally comprises a guide member 9 and a circular pressing member 11. The guide member 9 is formed with a conical bore 9a, and the pressing member 11 is powered by a hydraulic actuator (not shown). The diameter xe2x80x9cAxe2x80x9d of the largest upper end of the conical bore 9a is larger than the outer diameter xe2x80x9cBxe2x80x9d of the coiled body 5, and the diameter xe2x80x9cCxe2x80x9d of the smallest lower end of the conical bore 9a is equal to or slightly smaller than the inner diameter xe2x80x9cDxe2x80x9d of the metal case 7. Of course, the diameter xe2x80x9cAxe2x80x9d is larger than the diameter xe2x80x9cCxe2x80x9d. The pressing member 11 is sized somewhat smaller than the smallest lower end xe2x80x9cCxe2x80x9d of the conical bore 9a and has a flat lower surface.
For carrying out the press-fitting, at first, as is shown in FIG. 14A, the guide member 9 is correctly set on one open end of the metal case 7, and the coiled body 5 is raised and coaxially put into the conical bore 9a of the guide member 9 from the largest upper end of the bore 9a. Then, the pressing member 11 is put on a flat end face 5a of the coiled body 5 and pushed downward by a length of xe2x80x9cLxe2x80x9d by the force of the hydraulic actuator. With this pushing action, the coiled body 5 is thrust into the metal case 7, as is seen from FIG. 14B. Under passing through the smallest lower end of the conical bore 9a, the coiled body 5 is subjected to a certain shrinkage in diameter, which smoothes the insertion of the coiled body 5 into the metal case 7. After reaching a proper position in the metal case 7, the coiled body 5 is somewhat expanded resiliently due to a restoring force thereof, and thus the cylindrical outer surface of the coiled body 5 entirely contacts the cylindrical inner surface of the metal case 7. The unit thus assembled, namely, the assembled unit consisting of the coiled body 5 and the metal case 7, is then put into a vacuum furnace for the heat treatment.
However, the above-mentioned known technique has failed to provide the users with satisfied results for the following reasons. That is, as is understood from FIG. 15, when the coiled body 5 is pressed down in the conical bore 9a by the pressing member 11, a circumferential portion of the flat end face 5a of the body 5 is unsightly slid off from the major part of the flat end face 5a due to appearance of an annular dead zone xe2x80x9cSxe2x80x9d between the periphery 11a of the pressing member 11 and the sloped inner wall 9b of the conical bore 9a, which has no pressure applied thereto from the pressing member 11. In fact, during thrusting of the coiled body 5 in the conical bore 9a, the slid-off portion of the end face 5a is severely pressed between the pressing member 11 and the sloped inner wall 9b and thus squashed unsightly, which lowers not only performance of the product but also external appearance of the same.
It is therefore an object of the present invention to provide a device for press-fitting a coiled body into a cylindrical metal case, which is free of the above-mentioned shortcomings.
According to a first aspect of the present invention, there is provided a device for press-fitting a generally cylindrical body into a cylindrical case, the generally cylindrical body being subjected to reduction in diameter when applied with a certain external force from a radial direction. The device comprises a guide member formed with a vertically extending bore of which cross section gradually reduces in size with increase of a distance from a top of the bore toward a bottom of the same, the cross section of the bottom of the bore being slightly smaller than that of the generally cylindrical body, the guide member being adapted to be put on the cylindrical case having the bore of the guide member coaxially aligned with the interior of the cylindrical case; a pressing member which, when actuated, presses down the generally cylindrical body raised in the bore of the guide member thereby to thrust the raised generally cylindrical body into the cylindrical case through the bottom of the bore; and an actuator for actuating the pressing member, wherein the member includes a center base plate, at least two side plates positioned on both sides of the center base plate, a guide structure by which the side plates are radially movable in opposite directions with respect to the center base plate, and biasing members for biasing the side plates radially outward.
According to a second aspect of the present invention, there is provided a device for press-fitting a cylindrical coiled body into a cylindrical case, which comprises a guide member formed with a conical bore of which cross section gradually reduces in size with increase of a distance from a top of the bore toward a bottom of the same, the cross section of the bottom of the bore being slightly smaller than that of the coiled body, the guide member being adapted to be put on the cylindrical case having the bore of the guide member coaxially aligned with the interior of the cylindrical case; a pressing member which, when actuated, presses down the cylindrical coiled body raised in the bore of the guide member thereby to thrust the raised coiled body into the cylindrical case through the bottom of the bore; and an actuator for actuating the pressing member, wherein the pressing member includes a circular center base plate; two arcuate side plates positioned at both sides of the center base plate having concave sides thereof directed toward the base plate; a stay bolt held by the center base plate and having axially opposed end portions projected from the center base plate in opposite directions, the axially opposed end portions movably carrying the arcuate side plates; and two spring members each being compressed between the center base plate and corresponding one of the arcuate side plates to bias the arcuate side plate outward.